Detection of fatigue fissures in aircraft structures is a very onerous maintenance operation when the part to be inspected is not easily accessible and requires dismounting operations. One current solution consists in manually checking, by means of eddy currents, a crack initiating surface, which requires to dismount some structural elements. The problem lies thus in detecting the apparition of fatigue cracks and in determining their length and position without requiring dismounting operations.
Sensors, previously installed such as wire cutter sensors or eddy current sensors or even acoustical detection sensors, contribute to reduce the costs involved as they prevent the environment of the piece to be monitored from being dismounted during the checking operations. Any technology has however its own advantages and drawbacks.
A detector of the wire cutter type uses an electrically conducting wire stuck on the fissure initiating surface. This detector enables to detect the possible apparition of a crack by testing the electrical continuity of the conducting wire. The wire is cut when the crack extends at the point where it is stuck. This solution is disadvantageous in that it gives a binary indication and does not enable either to estimate the length of the crack or to locate it for the breaking is likely to appear anywhere along the length of the conducting wire.
The invention uses the wire cutter principle, the innovation lying in its pattern which notably enables to estimate both the length and position of the fissure. According to this new pattern, instead of having one wire in the wire cutter, a lot of wires are arranged and connected in two arrays. Both arrays can be moreover interconnected for simplification reasons. The arrays form then a mesh network, preferably in a perpendicular arrangement, in order to precisely locate the damage.